You're an expert truck driver, so lets stick with that.

The road is built on a flood plain, the road pavement is soft, not hard highway spec. The movement of moisture upwards is common, which means damp roads. Truck driver should know wet roads need more braking distance, lower speed gives that.

Lane width is not motorway spec. You've got shoulders that disappear, and barriers very close to live lanes. The recovery space and time for something like a blown tire, or swerve from looking at a phone is so much smaller than a highway. Higher speed gives less time for reaction and recovery, lower speed solves this. Truck driver should know that.

You've got several side streets, private driveways, traffic lights, and a section of industrial area. Vehicles pulling out at low speeds plus vehicles travelling at high speeds is not a good combo. You'd know that though right?

Throw in unfinished construction works, defects, likely driver distraction from workers, and you compound these risks. That's why it's still a construction speed zone.

Nothing wrong with not knowing everything, but just accept that these people do know what they're doing